1. Field of the Invention
The present invention relates to a battery heating device for an electric vehicle, which is designed for use in an electric vehicle having a heat-generating source such as a combustion heater.
2. Description of the Related Art
In an electric vehicle without a heat source such as an engine, the utilization of a combustion heater in order to heat the interior of the vehicle is known. (Refer to Japanese Utility Model Application Laid-Open No. 58-54903.) A brief description will now be provided hereinafter in connection with a structure disclosed in the above publication.
FIG. 7 illustrates this particular structure in which an unit case 102 is disposed within a vehicle interior 100. The unit case 102 houses a blower 104. An air inlet portion 106 and an air blowing portion 108 are located respectively upstream and downstream from the blower 104. The unit case 102 is further provided with: a chest-oriented blowing port 110; a defroster port 112; a leg-oriented blowing port 114; and, dampers for opening and closing these ports.
Meanwhile, a combustion heater 120 as well as a motor 118 are disposed within a motor room 116 which is located outside of the vehicle interior.
The above-noted unit case 102 and combustion heater 120 communicate with each other via a duct 122 so as to bring air from the unit case 102 into the heater 120. The combustion heater 120 is provided with a heated air blow-off port 124 on a side portion thereof. The heated air blowing port 124 communicates with one end of a heater duct 125. The other end of the heater duct 125 communicates with the interior of the unit case 102 at a location between the blower 104 and the air blowing portion 108. The combustion heater 120 has an exhaust pipe 126 mounted thereto so as to permit exhaust gases, which are produced by the heater 120, to be discharged outside of the vehicle.
According to the above construction, the combustion heater 120 is disposed within the motor room 116 that is located outside of the vehicle interior. Further, the combustion heater 120 and the unit case 102, which is located within the vehicle interior, communicate with each other via the heated air blowing port 124 and the heater duct 125 in such a manner as to permit heated air, which is subjected to heat by the heater 120, to be introduced into the unit case 102. This arrangement eliminates the need for considerable improvements in the unit case 102 to be made in order to combine the combustion heater 120 with the unit case 102. Further, a stench caused by the combustion of fuel such as kerosene can be prevented from lingering in the vehicle interior 100.
However, the construction disclosed in the above-noted publication is designed for the exclusive use of the combustion heater 120 for heating the vehicle interior 100. As a result, exhaust heat, which is unused for heating, is discarded as an exhaust gas in the air from the exhaust pipe 126 without being utilized. Thus, there is a problem in that the above structure makes no effective use of the exhaust heat from the combustion heater 120.
Further, by way of another example in the related art, the following construction will be described.
It is commonly known that a battery disposed in a vehicle will exhibit a reduced level of charging-discharging efficiency in low temperature environments. As a method of preventing a drop in efficiency, there is disclosed a structure for raising and maintaining the temperature of a battery. (For one example of the above, reference is made to Japanese Utility Model Application Laid-Open No. 60-192367.)
A brief description will now be provided in connection with the structure disclosed in the above publication.
FIG. 8 illustrates the above-identified structure in which a plate-shaped container 200 is provided for accommodating a battery 202. The container 200 is formed of a heat-insulating material. The container 200 has a planarshaped heater 204 removably attached to the base thereof, and as such, the battery 202 is received therein. The heater 204 has electrodes 206 and 208 mounted on both sides thereof (that is, the electrodes 206 and 208 are located on the inside of opposite side walls of the container 200). One of the electrodes, 206, is connected to a plug 212 via a fuse 210, while the other 208 is coupled to the same plug 212 via a thermostat 214.
According to the above structure, for charging of the battery 202 in low temperature environments, the plug 212 is inserted into an outlet and electricity is supplied to the electrodes 206 and 208 so as to heat the planer-shaped heater 204. As a result, heat is applied to the battery 202 which is sealingly placed on the heater 204, thereby improving charging efficiency.
However, the disclosed structure in the publication using the planar-shaped heater 204 presents the following disadvantages when used to elevate and maintain the temperature of a large-sized battery disposed in an electric vehicle.
That is, when the battery is charged a substantial increase in the consumption of electric power is required from an external power supply. This goes against the demand for saving electric power. In addition, the planar-shaped heater 204 is heated during traveling because the large-sized battery is used as a power source. Such heating results in a considerable increase in the amount of electric power required from a vehicle power supply (i.e., the battery), with a concomitant decrease in mileage of the electric vehicle per charging.